Electromagnetic radiation is a phenomenon in which energy moves in a sinusoidal waveform while an electric field and a magnetic field cooperate with each other, and the phenomenon is useful for wireless communication or electronic devices such as a radar. The electric field is generated by voltage and is easily shielded due to long distances or obstacles such as a tree while the magnetic field is generated by current and is inversely proportional to a distance but is not easily shielded.
A recent electronic device is sensitive to electromagnetic interference (EMI) generated by an internal or external interference source, and there is a possibility of a malfunction of the electronic device being caused by electromagnetic waves. Also, a user who is using an electronic device may be harmfully affected by electromagnetic waves generated by the electronic device.
Accordingly, there is a growing interest in electromagnetic wave shielding materials for protecting human bodies or components of an electronic device against electromagnetic waves emitted from an electromagnetic wave source or from an external source.
Such an electromagnetic wave shielding material is typically formed of a conductive material, and shields electromagnetic waves emitted toward the electromagnetic wave shielding material by reflecting the electromagnetic waves or directing the electromagnetic waves to the ground. An example of the electromagnetic wave shielding material may be a metal casing or a metal plate. Here, it is difficult for the electromagnetic wave shielding material to exhibit elasticity and it is not easy to change the electromagnetic wave shielding material to various shapes or to recover the electromagnetic wave shielding material once manufactured. Thus, the electromagnetic wave shielding material is difficult to employ in various application fields. In particular, it may be difficult for the electromagnetic wave shielding material such as a metal plate or a metal thin film to fully exhibit electromagnetic wave shielding performance because the electromagnetic wave shielding material is difficult to bring into close contact with a component requiring protection from an electromagnetic wave generating component or an electromagnetic wave source without a gap therebetween and also a crack may be generated due to bending at a stepped portion or an uneven portion.
In order to solve such a problem, an electromagnetic wave shielding material obtained by forming a conductive coating layer on a lightweight supporting member such as a polymer film has been recently produced. However, the electromagnetic wave shielding material has limitation on electromagnetic wave shielding performance in accordance with the limitation of an available area of the supporting member to be coated. Also, a film having a certain thickness or greater is insufficiently flexible, and thus may be difficult to bring into complete contact with components having a stepped portion or an uneven portion or to freely change in shape once manufactured in a specific shape. Even when the shape change is possible, a crack, a delamination, or the like may frequently be generated in a covered conductive coating layer during the shape change.